Ballpoint pens are well known as writing instruments and utilize a ball in the pen tip portion which rotates due to frictional force created in the writing motion to deposit ink on the writing surface. The pen tip structure of the ballpoint pen comprises a ball retaining shaft and a ball rotatably received in the ball retaining portion of the ball retaining shaft. The bottom of the ball retaining portion of the ball retaining shaft is formed into a cone-shape and an ink flow hole is bored in the center of the cone-shaped bottom.
There are problems in connection with the manufacture and writing performance and electrostatic action a ballpoint pens as follows.